Intermodal freight transport is a system of transporting intermodal containers by truck, rail, and ship. Most intermodal containers are governed by the International Standards Organization (ISO), and most containers are 8 feet wide and between 8.5 feet and 9.5 feet high. The most common lengths are 20 feet, 40 feet, 45 feet, 48 feet, and 53 feet (16 m), although other lengths exist.
Intermodal containers are carried on ships by stacking one on top of another, often as high as seven containers high. On trucks, the containers are carried on a chassis or semi-trailer, which is pulled by a tractor unit. The container is locked onto the chassis by twist locks, and the chassis is connected to the tractor unit by a fifth wheel hitch. On trains, the containers may be “single stacked” onto the bed of a train car (referred to as container on flatcar (COFC)), stacked one on top of another in a “double-stack” configuration, or the chassis with intermodal container may be loaded onto the bed of the train car (referred to as trailer on flatcar (TOFC)).
In practice, for example, a container may be loaded with goods and the container may be loaded onto a chassis. A truck conveys the container on the chassis to a rail terminal, where the container is lifted by one of several types of cranes onto a train car for conveying it efficiently over a long distance. The container may be offloaded onto a truck for a final trip (often referred to as drayage) to its final destination or for a trip to an ocean port, where the container is removed from the chassis and loaded onto a ship.